Unless I am mistaken, and I'm sure there will be a ton of people here who will correct me. There are no multi-alt-coin open source wallets for mobile. -snip-
There is Hodlerwallet[1] and also Trust wallet (owned by Binance) which used to be open source for iOS only but now, it seems like the GitHub repository has been archived[2] (but you should still be able to compile it yourself).